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Philippe
Asked: 2019-02-21 06:09:40 +0800 CST

Got a second modem, is my setup correct?

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I got a second modem to use with a second internet provider for my small business. To install that second modem on my network, I purchased a Dual Wan Router to take care of the load balancing.

Here is my setup (in yellow are my 2 new pieces of equipment):

Network Infrastructure

Previously, all was on subnet 3, no worries, but now it's 3 different subnets. DHCP is enabled on both Modems now, they provide an IP to the Router Wan ports, right? I want to know if this is correct, I am worried that the DHCP from both modems (subnet 1 and 2) will interfere with my DHCP server on subnet 3?

Thanks

networking

2 Answers

  1. Your setup is not OK as both modems are enabled in routing mode, you need them in bridge mode to prevent a double NAT issue. Call your ISP to make them work in the correct mode.

    It should be:

    [Public IP 1] ---- [Dual WAN ROUTER] ---- [Public IP 2]

    and below it should be 192.168.3.X for your LAN

    Make sure the router got the public IP, as in your schema I see 192.168.1.1 and 192.168.2.1, it should be your public IP there, not NATTed IP.

    The fact you double NAT block you on some routing issue.

    How you do a port forward or a DMZ ? How you do a VPN Tunnel ? How your dual WAN router will detect a failed ISP link ? as both WAN uplink gateway, that are NATed from your router will still ping (192.168.1.1 & 192.168.2.1). etc..

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  2. Each WAN interface on the router as well as the LAN interface are different Layer 2/3 networks. DHCP traffic, by default, will not cross those boundaries.

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